rcbs full length die and cam over...

[MagnumManiac]

Thanks so much for the reply. I think I get it.... so basically the case gets fully resized even if you do not cam over...

Yes, that is correct. The proper term is Partial FL Sizing. The reason a short chamber is so hard to size for is due to the case body being squeezed well before the shoulder is touched, this actually lengthens the head to shoulder dimension. So unless you are camming over, in some instances, there will be a gap between the shell holder top and die bottom. If you measure this with feeler gauges it will tell you how much you are NOT pushing the shoulder back by.
The best investment is either a Hornady head space comparator or the RCBS Precision Mic.

Cheers.

 

[GW Hunter]

Yes, that is correct. The proper term is Partial FL Sizing. The reason a short chamber is so hard to size for is due to the case body being squeezed well before the shoulder is touched, this actually lengthens the head to shoulder dimension. So unless you are camming over, in some instances, there will be a gap between the shell holder top and die bottom. If you measure this with feeler gauges it will tell you how much you are NOT pushing the shoulder back by.
The best investment is either a Hornady head space comparator or the RCBS Precision Mic.

Cheers.

I use the hornady comparator. I have always cammed over with my 7mm weatherby and that pushed my shoulder back .002. I guess I got lucky with that... The OP is in regard to a buddy's 300 weatherby and using the comparator to determine that the shoulder was being pushed back further than wanted. When time permits we will back the die out and start from there. Thanks again for the help.

 

[BountyHunter]

Cam over has nothing to do with enhancing accuracy or long case life. It is simply CYA by the mftrs to ensure the case will be fully sized close to factory specs for liability purposes. You want minimal but consistent sizing and ability to bump the shoulders .002. Understanding that and ability to control bump AND get case size at the base is key. That is about .200 up from the bottom. Sticky brass is normally at this .200 line. Competition shellholders are great.

 

[GW Hunter]

Just ordered a set of the Redding competition set...

 

[RegionRat]

The press ram mechanism has slop. The stiffness of the ram is non-linear and increases with load.

The potential position of that ram under a low load versus a high load (cam over) is why they have recommended cam-over as a general rule. That said, it is certainly possible to get good results without cam-over.

When you cam-over the position and stiffness of the ram is no loner a variable because you are positioning the die against the shell holder. When you don't cam over, the dispersion of that ram position is based on friction in your die pushing the slop out of the ram. If that works, you are done.

If that doesn't work for you, those incremental shell holders are the answer. Check your headspace and shoulder datum in either case.

 

[DUSTY NOGGIN]

Just ordered a set of the Redding competition set...

i knew you would, eventually

 

[DUSTY NOGGIN]

The potential position of that ram under a low load versus a high load (cam over) is why they have recommended cam-over as a general rule. That said, it is certainly possible to get good results without cam-over.

regionrat is correct , you can get good results without comp holders , but competition holders consistency is great

you know if you can get your bolt to fit that perfect snug fit - you are actually fitting the shoulder cone inside the chamber cone which in turn will center your bullet when sitting unfired in your chamber to the center line , if too loose like the neck will push again the opposite side of the ejector plunger